Systems and techniques are described that provide automated parking assistance for a vehicle. In some implementations, a parking assistance apparatus includes a frequency generator configured to generate a first frequency and a second frequency, and generate at least one synthesized frequency that is synthesized from the first frequency and the second frequency. The apparatus also includes a piezoelectric converter configured to, using piezoelectric effects, transmit ultrasonic waves having the at least one synthesized frequency, and receive reflected ultrasonic waves that result from the transmitted ultrasonic waves being reflected by an object. The apparatus also includes a filter unit configured to detect a predetermined frequency from the reflected ultrasonic waves.